ON ORCIIIDE.E AND Ai=;rLEriADK .E. 551
But as such granules, at the period of insertion, are either very few in number, or apparently altogether wanting, I an/still inclined to consider them rather as furnishing the nonrishment of the Tube than as being the essential agents in fecundation ; the really active particles in this function being probaljly much more minute.
'i'hese supplementary observations may be concluded with the remark, that althongh the descent of Tubes derived from the Pollen into the cavity of the Ovarium, and their insertion into that point of the Ovulum where the Radicle of the future Endjryo is seated, has been abso- lutely ascertained in several species of Orchide?c and in one of Asclepiadeao, and probably will be found in the whole of these two extensive families, yet it does not follow that this descent and insertion of Tubes should be expected to extend to all Phccnogamous plants ; for among these some structures of the female organ exist,' which hardly admit of this oeconomy.
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